Traditional Uses, Phytochemistry, and Pharmacological Properties of the Genus Blechnum—A Narrative Review

Blechnum L. is a genus belonging to the Blechnaceae family with 236 accepted species that grow in intertropical, subtropical, and southern temperate regions. Several species of the genus have long been used in folk medicines to treat a broad spectrum of ailments, including typhoid, urinary infections, influenza, wounds, pulmonary complaints, blisters, boils, and antihelmintic-related complications. So far, about 91 chemical compounds have been isolated from different parts of 20 Blechnum species. Among these metabolites, phenolic compounds, sterols, and fatty acids are the main constituents. Modern pharmacological investigations revealed several isolated compounds and extracts to exhibit exceptional biological properties including the antioxidant, antimicrobial, anti-inflammatory, anticancer, insecticidal, antitrematocidal and wound healing. In various tests, both quercetin-7′,3′,4′-trimethoxy and phytol metabolites showed potential antioxidant and antitrematocidal properties, while ponasterone exhibited insecticidal activity. Despite having a broad range of traditional medicinal benefits and biological properties, understanding the scientific connotations based on the available data is still challenging. This article presents a comprehensive review of the traditional uses, phytochemical compounds, and pharmacological aspects of the Blechnum species.


Introduction
Ancient traditional knowledge of plants' medicinal utility contributes significantly to bioprospecting by identifying plants for drug discovery. Many medicinal plants are effective remedies for diverse complaints, prompting increased screening for their therapeutic constituents [1,2]. In the past, pteridophytes (fern and fern-allies) were considered as significant sources of treatment against different disorders and for culinary purposes [3][4][5].
Natural agents with medicinal values have been extensively investigated in plants [10], and various studies have explored the phytocompounds and bioactivities of different Blechnum species. Blechnum is a novel source of alcohols, aldehydes, carotenoids, phenolic

Botanical and Taxonomic Description
Blechnum species are distinguished by erect rhizomes which occasionally creep/form short trunks. The rhizomes consist of unarticulated stipes covered with protective hairlike scales, and in most Blechnum, they tend to exist primarily as underground structures. Leathery fronds are monomorphic or dimorphic [7], while circinate venation, simple lamina, and sometimes 1-pinnatifid or 1-pinnate characterize their stalks and leaf blades ( Figure 1). The sterile and fertile fronds can either be pinnate or bipinnate (http://www. worldfloraonline.org, accessed on 11 April 2022). Rachis and costae are scaly and glabrous, whereas sori are paralleled next to costae and are borne on vascular commissures. They reproduce with spores as substitutes for seeds produced in bundles under the fronds. The spores are perine smooth to diversely winged or rugose, with reticulate perispore, and contain small papillae [7].

Distribution and Conservation Status
Blechnum species are broadly distributed in various parts of America, Europe, Africa, Australia, Asia, and several islands, including Hawaii, Mascarene, and Cunha among others (https://powo.science.kew.org/ accessed on 7 April 2022) [25] (Figure 2). They mainly occupy terrestrial, rocky areas and can exist as erect, climbing, or rarely epiphytic plants. In New Zealand, they are represented by about 18 indigenous species. In China, the Blechnum orientale (L.) C. Presl., is widespread in Fujian, Guangdong, Hainan, Hunan, Sichuan, Yunnan, Zhejiang, and neighboring areas (http://www.efloras.org accessed on 7 April 2022). Additionally, 15 primarily epiphytic and terrestrial Blechnum plants are widespread in Mexico [7], whereas 13 are common in Chile [26]. Most of these species are sub-cosmopolitan and inhabit the intertropical, subtropical, and southern temperate regions. The conservation status of about 145 recognized Blechnum species are yet to be evaluated

Distribution and Conservation Status
Blechnum species are broadly distributed in various parts of America, Europe, Afric Australia, Asia, and several islands, including Hawaii, Mascarene, and Cunha among ot ers (https://powo.science.kew.org/ accessed on 7 April 2022) [25] (Figure 2). They main occupy terrestrial, rocky areas and can exist as erect, climbing, or rarely epiphytic plan In New Zealand, they are represented by about 18 indigenous species. In China, the Blec num orientale (L.) C. Presl., is widespread in Fujian, Guangdong, Hainan, Hunan, Sichua Yunnan, Zhejiang, and neighboring areas (http://www.efloras.org accessed on 7 Ap 2022). Additionally, 15 primarily epiphytic and terrestrial Blechnum plants are widesprea in Mexico [7], whereas 13 are common in Chile [26]. Most of these species are sub-cosm politan and inhabit the intertropical, subtropical, and southern temperate regions. Th conservation status of about 145 recognized Blechnum species are yet to be evaluate

Traditional Uses of Blechnum Species
Blechnum species are used in Chilean Traditional Medicines (CTM), Traditional Indian Medicines (TIMs), and Traditional Chinese Medicines (TCMs) for various medicinal folklore [26][27][28]. The different types of Blechnum-derived formulations in the form of decoction, poultice, infusion, paste, and juice (Table 1) prepared from the fronds, rhizomes, whole plants, roots, and shoots are remedies for cancer, typhoid, influenza, inflammation, female sterilization, liver infections, intestinal wounds, stomach complaints, pulmonary illnesses, skin disorders, and urinary bladder complaints ( Figure 3, Table 1). Blechnum occidentale L., B. spicant (L.) Roth, B. serrulatum Rich, and B. orientale L. were found to be the most commonly utilized Blechnum species for medicinal purposes (Table 1).

Traditional Uses of Blechnum Species
Blechnum species are used in Chilean Traditional Medicines (CTM), Traditional Indian Medicines (TIMs), and Traditional Chinese Medicines (TCMs) for various medicinal folklore [26][27][28]. The different types of Blechnum-derived formulations in the form of decoction, poultice, infusion, paste, and juice (Table 1) prepared from the fronds, rhizomes, whole plants, roots, and shoots are remedies for cancer, typhoid, influenza, inflammation, female sterilization, liver infections, intestinal wounds, stomach complaints, pulmonary illnesses, skin disorders, and urinary bladder complaints ( Figure 3, Table 1). Blechnum occidentale L., B. spicant (L.) Roth, B. serrulatum Rich, and B. orientale L. were found to be the most commonly utilized Blechnum species for medicinal purposes (Table 1). Utilization of plants for medicinal purposes is attributed by their rich active ingredients [29]. They are utilized for clinical drug development as alternative natural agents to conventional chemotherapies. Traditional knowledge indicates that different parts of the Blechnum plants ( Figure 4) possess medicinal efficacy towards diverse sicknesses, thereby contributing to human health. Blechnum orientale was established as the most commonly used species to prepare folk medicines in the studied genus. The frequently used parts in the preparation of herbal medicines included fronds and rhizomes, while roots and shoots are less widely used ( Figure 4). Utilization of plants for medicinal purposes is attributed by their rich active ingredients [29]. They are utilized for clinical drug development as alternative natural agents to conventional chemotherapies. Traditional knowledge indicates that different parts of the Blechnum plants ( Figure 4) possess medicinal efficacy towards diverse sicknesses, thereby contributing to human health. Blechnum orientale was established as the most commonly used species to prepare folk medicines in the studied genus. The frequently used parts in the preparation of herbal medicines included fronds and rhizomes, while roots and shoots are less widely used ( Figure 4).

Traditional Uses of Blechnum Species
Blechnum species are used in Chilean Traditional Medicines (CTM), Traditional Indian Medicines (TIMs), and Traditional Chinese Medicines (TCMs) for various medicinal folklore [26][27][28]. The different types of Blechnum-derived formulations in the form of decoction, poultice, infusion, paste, and juice (Table 1) prepared from the fronds, rhizomes, whole plants, roots, and shoots are remedies for cancer, typhoid, influenza, inflammation, female sterilization, liver infections, intestinal wounds, stomach complaints, pulmonary illnesses, skin disorders, and urinary bladder complaints ( Figure 3, Table 1). Blechnum occidentale L., B. spicant (L.) Roth, B. serrulatum Rich, and B. orientale L. were found to be the most commonly utilized Blechnum species for medicinal purposes (Table 1). Utilization of plants for medicinal purposes is attributed by their rich active ingredients [29]. They are utilized for clinical drug development as alternative natural agents to conventional chemotherapies. Traditional knowledge indicates that different parts of the Blechnum plants ( Figure 4) possess medicinal efficacy towards diverse sicknesses, thereby contributing to human health. Blechnum orientale was established as the most commonly used species to prepare folk medicines in the studied genus. The frequently used parts in the preparation of herbal medicines included fronds and rhizomes, while roots and shoots are less widely used ( Figure 4). The fronds obtained from B. orientale are regarded as cure for intestinal wounds, pulmonary complaints, skin disorders, and urinary bladder infections. Additionally, those obtained from B. spicant are chewed to cure skin disorders, cancer, pulmonary, and stomach complaints, while B. serrulatum is used as a remedy for skin disorders. The rhizomes from B. orientale and B. serrulatum are also significant sources of traditional therapies for urinary bladder infections, typhoid, and intestinal worms (Table 1). Decoction prepared from the roots of B. spicant is used to cure diarrhoea, while the shoots obtained from B. orientale are pounded and the paste is applied to treat boils [30,31]. Oral ingestion of the entire plant of B. orientale has a medicinal relevance in the sterilization of women. Likewise, the whole plants of B. spicant are popular medicines against skin ailments in the United States of America [32]. They are externally applied to treat skin sores. [30] Roots Decoctions prepared from the roots are used as a remedy for diarrhea [30] United States of America Whole plant Treatment of skin ailments [32] B. orientale (L.) C. Presl.

Malaysia. Shoots
The shoots are pounded and used as a paste to cure boils [31] Fronds The fronds are ground in cow's milk to treat asthma [1] Applied in the form of a poultice to treat boils [31] Externally applied to cure blisters, boils, carbuncles, and sores The leaves are crushed and applied as medication for abscesses [31][32][33] India Fronds Urinary bladder complaints [8,34] Hot decoction prepared from pinnae is used for its antiseptic action or applied externally over a boil to release pus. [35] The extracted juice is used to treat intestinal Wounds. [36]

Rhizomes
It is orally administered to treat typhoid. [9,32] The prepared paste is applied to cure urinary bladder infections. [36] Philippines Fronds They are used for polynesia, diaphoretic, and operative actions [8,28] China Rhizomes Are used as an anthelminthic to cure intestinal worms [8,28]

Secondary Metabolites
Early phytochemical study of the Blechnum genus occurred in the 1960s, which revealed the existence of chlorogenic and blechnic acid in the leaves of B. spicant, B. orientale, B. discolor, and B. brasiliense [42]. Later, preliminary phytochemical studies identified numerous anthocyanidins from the leaves of B. procerum [17]. Other investigations in subsequent years resulted in isolation and identification of steroids, flavonols, flavones, lignans, fatty acids, phytosterols, diterpenes, sesquiterpenes, alcohols, aldehydes, carotenoids, and heterocyclic compounds ( Figure 5).

Secondary Metabolites
Early phytochemical study of the Blechnum genus occurred in the 1960s, which revealed the existence of chlorogenic and blechnic acid in the leaves of B. spicant, B. orientale, B. discolor, and B. brasiliense [42]. Later, preliminary phytochemical studies identified numerous anthocyanidins from the leaves of B. procerum [17]. Other investigations in subsequent years resulted in isolation and identification of steroids, flavonols, flavones, lignans, fatty acids, phytosterols, diterpenes, sesquiterpenes, alcohols, aldehydes, carotenoids, and heterocyclic compounds ( Figure 5). In the present study, a detailed investigation of phytochemicals derived from the Blechnum species revealed a broad spectrum of structurally diverse and biologically active metabolites. Ninety-one specialized metabolites encompassing 39 phenolic compounds, 25 sterols, 12 fatty acids, 5 terpenes, 4 alcohols, 3 aldehydes, 2 carotenoids, and a heterocyclic compound were isolated ( Table 2). The dominant specialized products were steroids, anthocyanidins, flavonoids, and fatty acids, whereas carotenoids, sesquiterpenes, and heterocyclic metabolites were the least isolated. Chemical compounds were primarily screened from leaves/fronds, rhizomes, whole plants, and aerial parts and are described based on the original sources. The major techniques used screen metabolites included Liquid Chromatography, Mass spectrometry (MS) and Nuclear Magnetic Resonance (NMR).

Phenolic Compounds
Phenolic compounds are among plants main classes of natural bioactive metabolites and are structurally distinguished by a single phenol unit, broadly grouped as simple phenols and polyphenols [43]. These metabolites were isolated from several Blechnum species, and 40 secondary metabolites are reported (Table 2), with some of their chemical structures depicted in Figure 6. In the present study, a detailed investigation of phytochemicals derived from the Blechnum species revealed a broad spectrum of structurally diverse and biologically active metabolites. Ninety-one specialized metabolites encompassing 39 phenolic compounds, 25 sterols, 12 fatty acids, 5 terpenes, 4 alcohols, 3 aldehydes, 2 carotenoids, and a heterocyclic compound were isolated ( Table 2). The dominant specialized products were steroids, anthocyanidins, flavonoids, and fatty acids, whereas carotenoids, sesquiterpenes, and heterocyclic metabolites were the least isolated. Chemical compounds were primarily screened from leaves/fronds, rhizomes, whole plants, and aerial parts and are described based on the original sources. The major techniques used screen metabolites included Liquid Chromatography, Mass spectrometry (MS) and Nuclear Magnetic Resonance (NMR).

Phenolic Compounds
Phenolic compounds are among plants main classes of natural bioactive metabolites and are structurally distinguished by a single phenol unit, broadly grouped as simple phenols and polyphenols [43]. These metabolites were isolated from several Blechnum species, and 40 secondary metabolites are reported (Table 2), with some of their chemical structures depicted in Figure 6.

Lignans
Lignans phytochemicals have been highly screened in various Blechnaceae species [52]. In the Blechnum genus, these compounds (4-7) were isolated from the fronds of B. orientale and B. spicant ( Table 2). The investigation by Wada et al. [15] assessed B. orientale extracts and detected various metabolites including blechnic acid, 7-epiblechnic acid, 8-epiblechnic acid, and brainic acid. Figure 6 shows the chemical structures of some of the isolated lignans.

Lignans
Lignans phytochemicals have been highly screened in various Blechnaceae species [52]. In the Blechnum genus, these compounds (4-7) were isolated from the fronds of B. orientale and B. spicant ( Table 2). The investigation by Wada et al. [15] assessed B. orientale extracts and detected various metabolites including blechnic acid, 7-epiblechnic acid, 8epiblechnic acid, and brainic acid. Figure 6 shows the chemical structures of some of the isolated lignans.

Sterols
Sterol metabolites have been highly isolated and identified in the family Blechnaceae [12,13,18]. They are isoprenoid derivatives with diverse composition existing as either free forms, conjugated, or steryl glycosides [59]. Sterol compounds with high structural diversity were isolated from numerous Blechnum plants (compounds 45-69) ( Table 2), and some of their structural diversity is represented in Figure 8. The phytoecdysteroids (compounds 45-56): fundamental analogues in insects as moulting hormones were isolated from the fronds of B. vulcanicum [14]. Similarly, several other constituents including ecdysone (45), ponasterone (56), and shidasterone (57), were also screened from dried leaves of different Blechnum species. Compound (56) and its synthesized derivatives exhibited receptor-binding activities towards the ecdysone receptor of Kc cells [60].

Fatty Acids
Fatty acids encompass saturated and unsaturated hydrocarbon chains of variable sizes, distinguished by the carboxyl group positioned at one end, and the methyl group at the inverse [61]. Numerous studies have reported several fatty acids from plants to be linked to various biological properties [62,63]. In the present investigation, 12 structurally The phytosterol compounds were also isolated from the whole plant extracts of B. orientale [12,13,18]. These are plant-derived fatty compounds with limited structural diversity and are cholesterol-related [10]. Numerous previous investigations reported the biological properties of the phytosterols, and nine compounds (66)(67)(68)(69) were isolated and identified primarily from the extracts of B. corralense, B. chilense, B. brasiliense, B. microphyllum. asperum, B. binervatum, B. mochaenum. blechnoides, B. hastatum, and B. penna-marina, B. magellanicum, B. arcuatum, and B. occidentale (Table 2).

Fatty Acids
Fatty acids encompass saturated and unsaturated hydrocarbon chains of variable sizes, distinguished by the carboxyl group positioned at one end, and the methyl group at the inverse [61]. Numerous studies have reported several fatty acids from plants to be linked to various biological properties [62,63]. In the present investigation, 12 structurally diverse fatty acid constituents (compounds 70-81) were isolated from the leaves and whole plants of different Blechnum plants [11,12,23], and their representative chemical structures shown ( Figure 9, Table 2). The phytochemical analysis by Maria et al. [12] revealed several fatty acid components (70-78) from dichloromethane and hexane fractions prepared from the leaves of B. binervatum, B. occidentale, and B. brasiliense. Similarly, two fatty acid components; 1,2,3-propanetricarboxylic acid 2-hydroxy-, triethyl ester (79), and hexanedioic acid, mono (2-ethylhexyl) ester (80) were isolated from B. orientale extracts and registered to exhibit numerous medicinal properties including antimicrobial, anti-inflammatory, antioxidant, antiulcer, and nematicidal [23].

Pharmacological Activity
Beneficial medicinal plants, as demonstrated by the presence of specialized metabolites, are ideal resources for revealing novel discoveries for therapeutic advances and breakthroughs. Medicinal plants serve as alternatives to modern medicines in most of the world's populations [20]. Some Blechnum plants are significant sources of traditional remedies for different illnesses (Table 1), which have recently motivated the exponential increase in pharmacological research. Crude extracts and several specialized products isolated from this genus exhibit a wide range of biological activities, including the antioxidant, antimicrobial, anti-inflammatory, anticancer, wound healing, insecticidal, and antitrematocidal activities described in this section.

Antioxidant Activity
Antioxidants are chemical compounds that play critical roles in preventing or delaying lipid peroxidation and scavenging free radicals, which are major causes of diseases in humans and other animals [65]. The ability of medicinal plants to scavenge 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radicals has been reported in the Blechnaceae family [66][67][68]. Several studies evaluated the antioxidant properties of various extracts obtained from the Blechnum plants. The fractions at 2-1000 µg/mL prepared from the leaves of B. orientale showed significant scavenging effects, comparable to the positive controls. The ethyl acetate fraction (EAf) displayed the strongest activity, equivalent to Trolox-C (IC50 8.6 µg/mL) and greater than butylated hydroxytoluene (BHT) (IC50 17.2 µg/mL) and tocopherol (IC50 12.0 µg/mL) controls [2].

Pharmacological Activity
Beneficial medicinal plants, as demonstrated by the presence of specialized metabolites, are ideal resources for revealing novel discoveries for therapeutic advances and breakthroughs. Medicinal plants serve as alternatives to modern medicines in most of the world's populations [20]. Some Blechnum plants are significant sources of traditional remedies for different illnesses (Table 1), which have recently motivated the exponential increase in pharmacological research. Crude extracts and several specialized products isolated from this genus exhibit a wide range of biological activities, including the antioxidant, antimicrobial, anti-inflammatory, anticancer, wound healing, insecticidal, and antitrematocidal activities described in this section.

Antioxidant Activity
Antioxidants are chemical compounds that play critical roles in preventing or delaying lipid peroxidation and scavenging free radicals, which are major causes of diseases in humans and other animals [65]. The ability of medicinal plants to scavenge 2,2-diphenyl-1picrylhydrazyl (DPPH) free radicals has been reported in the Blechnaceae family [66][67][68]. Several studies evaluated the antioxidant properties of various extracts obtained from the Blechnum plants. The fractions at 2-1000 µg/mL prepared from the leaves of B. orientale showed significant scavenging effects, comparable to the positive controls. The ethyl acetate fraction (EAf) displayed the strongest activity, equivalent to Trolox-C (IC 50 8.6 µg/mL) and greater than butylated hydroxytoluene (BHT) (IC 50 17.2 µg/mL) and tocopherol (IC 50 12.0 µg/mL) controls [2].

Antimicrobial Activity
A rigorous search for new antibiotics has been necessitated by the prompt development of drug-resistant strains of pathogens. Medicinal plants resources are potential candidates as antimicrobial agents, prompting extensive screenings to test their antimicrobial efficacy. In the present review, B. orientale was found to be an outstanding source of natural antimicrobial agents, and various investigations are discussed below.
Additionally, the acetone extract obtained from the leaves of B. orientale was tested against S. aureus, Bacillus subtilis, Klebsiella pneumonia, Salmonella typhi, Streptococcus pyogenes, Proteus vulgaris, Pseudomonas sp., and Serratia sp. at a dosage of 1 mg/disc [28]. Remarkable antibacterial activity was revealed by the maximum inhibition of P. vulgaris (MIC 0.025 mg/mL), while minimum zones were exhibited against B. subtilis and S. aureus. In another investigation, the leaves extract of B. orientale was tested against eight strains of bacterias encompassing M. luteus, B. cereus, S. aureus (Gram-positive), Escherichia coli, Pseudomonas aeruginosa, Salmonella choleraesuis, Enterobacter aerogenes, and Klebsiella pneumonia (Gram-negative), with methanol and streptomycin (10 mg) used as positive and negative controls, respectively. The three bacteria; M. luteus (48% inhibition, MID 500 mg/disc), B. cereus (57% inhibition, MID 500 mg/disc), and S. aureus (63% inhibition, MID 250 mg/disc), exhibited significant activities, which were comparable to streptomycin, while no inhibitions were reported for Gram-negative bacteria [72]. Insensitivity of the Blechnum extracts against the latter indicate the higher resistance of Gram-negative bacteria towards plant extracts compared to Gram-positive strains, consistent with other studies [73,74].
Finally, bacterial pathogens including S. aureus, B. subtilis, S. typhi, M. luteus, P. aeruginosa and E. coli were clinically isolated in an in-vitro antimicrobial efficacy trial using B. orientale extracts (pet-ether, chloroform, methanol, and aqueous) at 500 and 1000 µg/mL concentration. The extracts displayed remarkable inhibitions against E. coli at both 500 µg/mL (16.13 ± 0.09-20.2 ± 0.17 mm) and 1000 µg/mL (21.7 ± 0.16-24.0 ± 0.18 mm) concentrations, while P. aeruginosa showed significant inhibitions (11.0 ± 0.06-14.13 ± 0.09 mm) at 500 µg/mL. However, no inhibitions were exhibited by S. typhi and the rest of the Gram-positive bacterias. Both extracts were sensitive against Gram-negative bacteria, with strong sensitivity at 250 µg/mL observed in chloroform and aqueous extracts against E. coli. In addition, the maximum inhibitory concentration of both extracts against P. aeruginosa was exhibited at 250 µg/mL [19]. Thus, Blechnum plants are potential antibacterial agent in development of alternative phytomedicines, and this justifies the popular traditional medicinal uses in the treatment of bacterial-related infections.

Antifungal Activity
In Blechnum genus, the extracts obtained from B. orientale were studied for antifungal activity. Deepa et al. [19] obtained various extracts prepared from the fronds at the concentration of 500 and 1000 µg/mL against Candida albicans and Aspergillus flavus. The results showed high antifungal activity against C. albicans at the concentration of 1000 µg/mL with 11.0 ± 0.09-12.13 ± 0.09 mm zones of inhibition compared to the standard fluconazole-25.12 mm, while no inhibition activity was indicated towards A. flavus.

Anti-Inflammatory Activity
Inflammation might occur in the absence of illness (sterile inflammation) or as a selfdefence mechanism against pathogens when the body responds to tissue injury [75][76][77]. The inflammation-related illnesses are commonly treated with steroidal or non-steroidal chemical medicines in pharmaceuticals [78]. However, these drugs have been shown to potentially induce toxicity and diverse side effects [79][80][81]. Thus, exploring new analgesic and anti-inflammatory agents with fewer negative effects is of great concern.
The various tests such as writhing, formalin, tail flick, paw oedema, and leukocyte migration were conducted to evaluate the anti-inflammatory and antinociceptive activities of the extracts derived from B. occidentale [3]. The mice were intraperitoneally (IP) and orally administered with the prepared extracts at the concentration ranges of 0.01-100 mg/kg and 100-400 mg/kg, respectively. The orally administered extracts dose-dependently induced writhing and showed significant antinociceptive effects. Additionally, the paw oedema induced by carrageenan and neutrophil migration was potentially reduced on intraperitoneal treatment with no cytotoxicity (p < 0.01).
In another study, Fasolo et al. [82] used the adult zebrafish to investigate the antiinflammatory properties of rosmarinic acid, a bioactive molecule derived from the fronds of B. brasiliense by lipopolysaccharide induction model. In this trial, the intraperitoneal (i.p.) injection of lipopolysaccharides (LPS) was administered to induce a neuroinflammation cascade. The results indicated the promotion of TNF-α and IL-1β in zebrafish brain content within 24 h. Co-treatment with rosmarinic acid at the concentration of 2.5-7.5 mg/kg, and further LPS administration, showed the capability of the latter compound to reduce TNF-α and IL-1β levels. The compound exhibited a dose-dependent anti-inflammatory effects, with the highest concentration (7.5 mg/kg), greatly decreasing the TNF-α levels (p = 0.0026) and IL-1β levels (p = 0.0053) 6 h after the induction of LPS, while they were reduced in lower doses and somewhat prevented their augmentation. The investigated properties validate the traditional use of Blechnum species in treating various ailments, including inflammations, liver, urinary, and pulmonary infections.

Anticancer Activity
Cancer is among the leading cause of mortality today, and is characterized by uncontrolled growing and spreading of abnormal cells [83]. The burden of cancer incidence and deaths are globally accelerating with about 2.3 million new cases of female breast cancer reported recently to be among the most commonly diagnosed type of cancer infection [84], which results in nearly 40,000 deaths annually. Thus, various medicinal plants in the Blechnaceae family, such as the Blechnum plants, were tested for cancer treatment to replace modern medicines. The in vitro cytotoxic potential of different extracts ranging from 0.1 to 100 µg/mL concentration were prepared from the leaves, stems, and roots of B. orientale and investigated against the human breast cancer cell line (MCF-7wt.). Cells with oestrogen receptors (ER+) were models for assessing the events linked to chemotherapic responses of MCF-7wt. The cell viability of the roots, leaves, and stems extracts were 31.47%, 81.44%, 89.05% respectively. The extracts obtained from roots displayed cytotoxicity values of IC 50 value of 32.07 ± 7.85 µg mL −1 , with 19.1% cell mortality, and thus can be a vital source of cancer treatment [20].
Furthermore, Lai et al. [2] tested the various extracts obtained from B. orientale against four cancer cell lines. The butanol (Butf) (IC 50

Wound Healing Activity
Wounds are caused by physical, thermal, chemical, or microbial damage to living tissues, disrupting their normal functioning [85]. The wound-healing process is currently facing clinical challenges due to the observed inconsistencies at various stages [86]. The absence of effective modern medicines has instigated intense searches for alternative novel natural medicines. Many medicinal plants were scientifically proven as sources of therapeutics for wounds [87], consistent with the holistic approach by traditional systems toward curing various wound-related illnesses. However, only a single species in the Blechnum genus has been assessed for its wound-healing properties. Since antiquity, B. orientale has long been reported as a vital source of traditional remedies against wound-related complaints [31,32]. Pharmacogical studies support the traditional therapeutic assertion against skin-related ailments.
Lai et al. [22] used an in vivo assay technique to investigate the effects of water extracts obtained from the leaves of B. orientale on Sprague-Dawley rats wound healing. In this study, the animals were segregated into four groups, each consisting of six specimens, and were intraperitoneally administered with either 100 mg/kg of ketamine or 10 mg/kg xylazine in order to anesthetize them, followed by the subcutaneous injection of 5 mg/kg carprofen as an analgesia. The treatment groups were segregated into 1% and 2% water extracts and monitored daily. Controls were applied with the dosage of 0.20 g/wound once a day until healing/14 days. The size of wounds and the mean duration of epithelisation were significantly reduced in both cases. The 2% extract exhibited outstanding activities with wound contraction of 128.7 ± 13.4-0.8 ± 0.9 mm 2 within 14 days, compared to 1% extract (139.7 ± 15.4-8.8 ± 0.9 mm 2 ), which indicated interesting dose-dependent wound healing properties (p < 0.001) compared to both negative (163.7 ± 10.4-25.5 ± 6.4 mm 2 ) and positive (133.7 ± 12.0-5.0 ± 0.9 mm 2 ) controls dressed in the base cream and 10% povidoneiodine, respectively. Additionally, the collagen synthesis was higher in the group treated with 2% water extract compared to the vehicle group and 1% extract. More investigations are warranted to strongly authenticate the medicinal uses of Blechnum species.

Insecticidal Activity
Novel environmentally safe natural products from plants have been extensively exploited in search of alternative agents for synthetic pesticides aimed to effectively control insects [88,89]. Numerous medicinal plants were revealed to have significant insecticidal properties in the Blechnaceae family [18,90]. Monsalve et al. [26] used the ethyl acetate (EtOAc) and n-hexane (HX) fractions obtained from B. chilense to investigate it's insecticidal potential. Drosophila melanogaster was treated with the prepared extracts at 200 to 800 ppm concentration ranges, while distilled water was used as a control. The extracts concentration-dependently affected development of the studied insects and induced larval mortality by 66.7% (EtOAc) and 63.3% (HX). At lower concentrations, the fractions showed either less mortality or less harmful effects. The isolated compound (ponasterone) was linked to the insecticidal activity of B. chilense. This metabolite showed a high affinity for ecdysone receptors found in Kc cells of D. melanogaster [60]. In addition, the prepared EtOAc extract concentration at 500 µg/mL obtained from the leaves of B. chilense showed toxicity (insecticidal efficacy) against Galleria mellonella larvae and induced premature pupal stage, exhibiting regulatory properties towards the development of larvae. The phytoecdysteroides compounds were potential constituents associated with the insecticidal property of Blechnum species [21]. Ecdysteroids hormones found in insects play a novel role in their metamorphosis. Since phytoecdysteroids metabolites have structural similarities with insect ecdysteroids hormones, plants containing this compounds act as remarkable anti-feedant agents with deterrent activities, and may instigate pathophysiological effects and organism death [91][92][93].

Antitrematocidal Activity
Anthelmintic resistance has become a global challenge, especially among farmers due to the parasitism which develops when synthetic anthelmintic drugs are frequently used. Alternatively, natural antiparasitic plant-derived products have been reported to effectively overcome resistance [5,94,95]. Pteridophytes have been demonstrated to be potential sources of trematodicidal drugs. Selected medicinal ferns, including B. orientale, were investigated for their in vitro antitrematodal activities [5]. The prepared eluates at 1 to 5 mg/mL concentration were examined against Gastrothylax crumenifer by incubating the test group with test extracts for one hour while recurrently observing their mobility, paralysis, and death. In addition, oxyclozanide (0.25 g/25 mL) was used as a standard control while a Hedon-Fleig (HF) salt solution was used as a negative control. The extracts showed the evidence of concentration-dependent increase in trematodicidal activities, and all amphistomes were killed at 5 mg/mL, similar to oxyclozanide, at the first ten minutes of incubation. The absence of mortality was reported for the entire incubation period at 1 mg/mL, while the concentration between 2-4 mg/mL caused partial mortality.
Devi et al. [23] performed an in vitro bioassay to assess the trematocidal potency of the extracts prepared from the whole plant of B. orientale against G. crumenifer. The test groups (25 amphistomes) were incubated with 25 mL of the extract fractions ranging from 1 to 5 mg concentration. In contrast, 0.25 g/25 mL of oxyclozanide was used as a control and visually observed at regular intervals for their mobility. Qualitative analysis indicated that the ethanol extracts concentration-dependently exhibited remarkable trematocidal activities against G. crumenifer. The most potent effects observed by duration taken to kill the trematodes were displayed at 5 mg concentration and were not comparable to oxyclozanide control. The screened phytochemical compounds, including quercetin-7 ,3 ,4 -trimethoxy (compound 12), and phytol isomer (42), were associated with the antitrematocidal efficacy of B. orientale. These specialized metabolites targeted the tegumental regions, which caused varied changes in enzymes at predilection sites. The shifts in tegumental enzymes restricted the metabolic action of trematodes resulting in the death of worms. However, more in vitro and in vivo investigations are essential to authenticate Blechnum species as vital sources of novel anthelmintic plant-derived drugs.

Other Activities
In addition to the above-mentioned biological activities, B. orientale has been shown to have significant inhibitory activity (EC 50 = 65.78 µg/mL) against α-glucosidase when compared to the myricetin control. As a result, this plant could be an interesting source of natural antidiabetic agents [96].
In the Blechnum genus, several species including B. orientale, B. binervatum, B. brasiliense, and B. chilense were reported to have pharmacological relevance (Figure 11). Blechnum orientale was widely studied, followed by B. occidentale and B. brasiliense, respectively, while B. chilense and B. binervatum were least studied. The reported biological properties including antioxidant, antimicrobial, anti-inflammatory and antinociceptive, wound healing, anticancer, and antitrematocidal activities concern different ailments and support the traditional assertion as treatments for influenza, typhoid, pulmonary infections, cancer, skin illnesses, inflammation, and intestinal wounds.
Pharmaceuticals 2022, 14, x FOR PEER REVIEW 22 In the Blechnum genus, several species including B. orientale, B. binervatum, B. br ense, and B. chilense were reported to have pharmacological relevance (Figure 11). B num orientale was widely studied, followed by B. occidentale and B. brasiliense, respectiv while B. chilense and B. binervatum were least studied. The reported biological prope including antioxidant, antimicrobial, anti-inflammatory and antinociceptive, wound h ing, anticancer, and antitrematocidal activities concern different ailments and suppor traditional assertion as treatments for influenza, typhoid, pulmonary infections, can skin illnesses, inflammation, and intestinal wounds.

Conclusions
In the present review, we compiled information on the chemical constituents biological activities of the Blechnum species. This genus encompasses several medicin significant plants with numerous specialized metabolites such as alcohols, aldehydes rotenoids, phenolic compounds, fatty acids, sterols, and terpenoids. A wide range of p macological effects such as antioxidant, antimicrobial, anti-inflammatory, antican wound healing, insecticidal, and antitrematocidal properties were exhibited by the p extracts and isolated metabolites. Several terpenoids and flavonoids metabolites wer sociated with antioxidant, antitrematocidal, and insecticidal activities. However, the p macological activities of most specialized metabolites listed in this review have yet t investigated.
Although the genus has reported interesting medicinal uses, there are still sev gaps that limit understanding of the scientific implications of several medicinally u Blechnum species. Foremost, only 20 of the 236 recognized species in the genus Blech have been evaluated for phytochemistry and bioactivities, while numerous other spe are still unexplored. Secondly, most pharmacological analyses centered on crude extr with no emphasis on the specific metabolites associated with biological activities. Thir in vitro models were mainly explored in assessing the pharmacological properties, only a few studies employing the in vivo systems. In addition, the observed bioactiv were mainly random screenings with no link between traditional uses and pharmaco ical activities. Lastly, only a single report described the underlying modes of actio bioactive metabolites with pharmacological effects. These afore-mentioned aspects a ciated with the medicinal uses of the Blechnum species necessitate further investigat to warrant their pharmaceutical applications.
Importantly, the present review demonstrates the scientific basis for some of the dicinal uses of a variety of Blechnum species and supports their traditional therape uses as remedies for various illnesses, validated by the majority of the pharmacolo

Conclusions
In the present review, we compiled information on the chemical constituents and biological activities of the Blechnum species. This genus encompasses several medicinally significant plants with numerous specialized metabolites such as alcohols, aldehydes, carotenoids, phenolic compounds, fatty acids, sterols, and terpenoids. A wide range of pharmacological effects such as antioxidant, antimicrobial, anti-inflammatory, anticancer, wound healing, insecticidal, and antitrematocidal properties were exhibited by the plant extracts and isolated metabolites. Several terpenoids and flavonoids metabolites were associated with antioxidant, antitrematocidal, and insecticidal activities. However, the pharmacological activities of most specialized metabolites listed in this review have yet to be investigated.
Although the genus has reported interesting medicinal uses, there are still several gaps that limit understanding of the scientific implications of several medicinally used Blechnum species. Foremost, only 20 of the 236 recognized species in the genus Blechnum have been evaluated for phytochemistry and bioactivities, while numerous other species are still unexplored. Secondly, most pharmacological analyses centered on crude extracts, with no emphasis on the specific metabolites associated with biological activities. Thirdly, in vitro models were mainly explored in assessing the pharmacological properties, with only a few studies employing the in vivo systems. In addition, the observed bioactivities were mainly random screenings with no link between traditional uses and pharmacological activities. Lastly, only a single report described the underlying modes of action of bioactive metabolites with pharmacological effects. These afore-mentioned aspects associated with the medicinal uses of the Blechnum species necessitate further investigations to warrant their pharmaceutical applications.
Importantly, the present review demonstrates the scientific basis for some of the medicinal uses of a variety of Blechnum species and supports their traditional therapeutic uses as remedies for various illnesses, validated by the majority of the pharmacological properties. Further investigations are required to extensively screen the specialized metabolites and investigate their biological activities to bring new fascinating findings and expound on the scientific basis of Blechnum for safe clinical application.